Switching Transistors Research Articles

Cleanroom-Free Direct Laser Micropatterning of Polymers for Organic Electrochemical Transistors in Logic Circuits and Glucose Biosensors.

Organic electrochemical transistors (OECTs) are promising devices for bioelectronics, such as biosensors. However, current cleanroom-based microfabrication of OECTs hinders fast prototyping and widespread adoption of this technology for low-volume, low-cost applications. To address this limitation, a versatile and scalable approach for ultrafast laser microfabrication of OECTs is herein reported, where a femtosecond laser to pattern insulating polymers (such as parylene C or polyimide) is first used, exposing the underlying metal electrodes serving as transistor terminals (source, drain, or gate). After the first patterning step, conducting polymers, such as poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), or semiconducting polymers, are spin-coated on the device surface. Another femtosecond laser patterning step subsequently defines the active polymer area contributing to the OECT performance by disconnecting the channel and gate from the surrounding spin-coated film. The effective OECT width can be defined with high resolution (down to 2µm) in less than a second of exposure. Micropatterning the OECT channel area significantly improved the transistor switching performance in the case of PEDOT:PSS-based transistors, speeding up the devices by two orders of magnitude. The utility of this OECT manufacturing approach is demonstrated by fabricating complementary logic (inverters) and glucose biosensors, thereby showing its potential to accelerate OECT research.

Exploration of structural influences on the ferroelectric switching characteristics of ferroelectric thin-film transistors.

In this paper, quantitative analysis was performed focusing on the structural effect on the ferroelectric switching of ferroelectric thin-film transistors (FeTFTs). FeTFTs and ferroelectric capacitor (FeCap) test element groups (TEGs) were designed and fabricated, and positive-up-negative-down (PUND) measurements were performed to analyze the switching characteristics of ferroelectric films in various structures constituting an FeTFT. It was verified that TiN/HZO/a-IGZO/Mo (MFSM, FeTFT source/drain contact) mostly contributed to the memory operation of an FeTFT, while TiN/HZO/a-IGZO (MFS, FeTFT channel) exhibits one-time memory operation with irreversible polarization switching. In addition, the switching characteristics of MFSM and MFS were different from those of MFM, especially after a few cycles, related to the oxygen vacancy migration between a-IGZO channels and HZO films. The extracted 2Pr values for MFS, MFSM and TiN/HZO/Mo (MFM, FeTFT source/drain parasitic capacitor) were 38, 28 and 20 [μC cm-2], respectively. Based on the operation differences according to the device structure, it was found that irreversible switching in the MFS region (channel) causes a rapid decrease in the memory window after the first switching in an FeTFT and degradation of a-IGZO and HZO films in the MFSM region (contact) including oxygen vacancy exchange and related defect generation causes subthreshold slope increases and negative threshold voltage shifts as cycling stress was applied.

(Invited) In-Situ MOCVD Etching of GaN Using XeF2 for Selective-Area-Epitaxial-Regrowth of p-Type GaN for High Voltage PN Diodes

PN diodes with multi-kilovolt breakdown voltages have been demonstrated to great than 6 kV in GaN, validating the device potential predicted by the intrinsic material properties of III-nitride semiconductors. However, power control circuits also require switching transistors such as junction field effect transistors (JFETs) and practical diodes such as merged PIN Schottky (MPS) diodes. Such devices usually employ selective areas of p-type semiconductor surrounded by n-type material and require the formation of PN junctions with low reverse leakage current. Selective-area p-type doping in Si and SiC based power devices is typically achieved using implantation and thermal annealing to form the p-type areas. Ion implantation of Mg in GaN has demonstrated p-type conductivity, but this process requires specialized equipment for the high-pressure and high-temperature activation of Mg dopants. We have investigated selective-area-regrowth (SArG) to epitaxially grow p-type GaN as an alternative to dopant implantation. Successful PN diode formation by SArG requires a process to remove residual crystalline damage resulting from the ex-situ inductively coupled plasma (ICP) etch typically used to form the p-well, as well as a method to remove the elevated level of Si found at the regrowth interface of a surface that had been exposed to air. For the case of SArG of p-GaN on air-exposed, blanket ICP etched n-type GaN, we present the novel use of a fluorine-based precursor (XeF2) for in-situ etching of GaN in the MOCVD chamber. Unlike chlorine (TBCl and CCl4) and bromine (CBr4) -based precursors we have studied; we obtained a smooth surface following in-situ fluorine etching of air-exposed GaN. Schottky barrier diodes (SBDs) formed by shadow mask evaporation on in-situ fluorine etched n-GaN that had been previously ICP etched showed reverse leakage currents to -40 V that are equal to those of SBDs formed on as-grown n-GaN layers. The in-situ fluorine/ICP etched Schottky diodes had reverse leakage currents more than 3 orders of magnitude lower than those formed on n-GaN layers that had only experienced ICP etching. This suggests that the in-situ fluorine etch was effective at removing the residual damage from the ICP etch process. Furthermore, we discuss the use of in-situ fluorine etching to reduce the concentration of Si at the regrowth interface required to form PN junctions with low reverse leakage current. This work was supported in part by the Advanced Research Projects Agency – Energy (ARPA-E), U.S. Department of Energy under the PNDIODES program directed by Dr. Isik Kizilyalli, and in part by the US Department of Energy (DOE) Vehicle Technologies Office (VTO) under the Electric Drive Train Consortium. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. The views expressed in the presentation do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

(Invited) Switching Characteristics of GaN Power Transistors

A shorter switching time is one of the key advantages of GaN power devices over Si IGBTs. [1] In this paper, we report on the simulation of GaN power transistor switching and investigate the effect on the switching time novel design approaches ranging from the gate edge engineering (beyond just using field plates [2] for optimizing the voltage distribution in the drain-to-gate spacing to using the quantum well channel designs [3] that lead to the electron wave function penetration into wide band gap cladding layers with the commensurate increase in the breakdown voltage while keeping the advantage of high mobility in the device channel. We also report on the effect of a low conducting passivation for smoothing or even eliminating the sharp maximum of the electric field in the vicinity of the gate and field plate edges on switching time.[4] Additional contacts in the drain-to-gate spacing for the field control and variable doping implants could also decrease the switching time. Further optimization could be achieved with the perforated channel designs [5] decreasing the parasitic series resistance and improving the heat dissipation.[1] A. Tüysüz, R. Bosshard, and J. W. Kolar, erformance Comparison of a GaN GIT and a Si IGBT for High-Speed Drive Applications, Proceedings of the International Power Electronics Conference - ECCE Asia (IPEC 2014), Hiroshima, Japan, May 18-21, 2014[2] S. Karmalkar, M. S. Shur, G. Simin and M. A. Khan, Field-Plate Engineering for Heterostructure Field Effect Transistors, IEEE Trans. ED, 52, 12, pp. 2516- 2532, December (2005)[3] M. Dyakonov and M. S. Shur, Consequences of Space Dependence of Effective Mass in Heterostructures, J. Appl. Phys. Vol. 84, No. 7, pp. 3726-3730, October 1 (1998)[4] G. Simin, M. Shur and R. Gaska, SETI-0070: Semiconductor device with low-conducting field-controlling element App. No 13/396,059, November 19, 2013 as US Patent No. 8,586,997[5] G. Simin, M. Gaevski, M. Shur, R. Gaska, Perforated Channel Field Effect Transistor, US patent 9,467,105, October 11, 2016

A review of crosstalk polymorphic circuits and their scalability

Using a control variable, the functionality of Polymorphic circuits can be modified, making them adaptable and useful for reconfiguring circuit behavior — all the way from gate level to system level. State-of-the art polymorphic circuits are based on custom non-linear circuit design or emerging devices such as ambipolar FET, configurable magnetic devices etc. While some of these approaches are inefficient in performance, others involve exotic devices. The Crosstalk computing based polymorphic circuits offer a fresh perspective. In Crosstalk, the interconnect interference between nanoscale metal lines is intentionally engineered to exhibit the programmable Boolean logic behavior. This approach relies on the coupling between metal lines and not on the transistors for computing, resulting in better scalability, security by obscurity, and fault tolerance by reconfiguration. Our novel approach is backed by the mathematical formulation that conveys the rationale to generalize and achieve a wide variety of polymorphic circuits. Our experiments, including design, simulation, and Power Performance Area (PPA) characterization results indicate that crosstalk circuits provide significant improvement in transistor count (about 3x), switching energy (2x), and speed (1.5x) for polymorphic logic circuits. In the best-case scenario, the transistor count reduction is 5x. This paper presents Crosstalk computing’s fundamentals, polymorphism and the scalability aspects to compete/co-exist with CMOS for digital logic implementations below 10 nm. Our scalability study uses Open Source 7 nm PDK, considers all process variation aspects and accommodates worst-case scenarios. The study results for various benchmark circuits show that the Crosstalk technology is a viable alternative to CMOS for digital logic implementations below 10 nm, having 48% density, 57% power, and 10% performance gains over equivalent CMOS counterparts. Finally, we compare Crosstalk Polymorphic Circuit design technique with similar approaches described in related works and discuss its features and constraints.

Open circuit fault diagnosis of three‐phase inverter based on SR‐WOA‐ELM

SummaryTo ensure smooth power exchange in a three‐phase inverter, it is important to accurately detect the faults of insulated gate bipolar transistor (IGBT) switches. However, the fault characteristics of power tubes are complex, the fault diagnosis results are affected by the load, and the recognition accuracy of some fault diagnosis models is low. To tackle this issue, this paper proposes an inverter open circuit fault diagnosis method named SR‐WOA‐ELM, which integrates signal reconstruction (SR), the whale optimization algorithm (WOA), and an extreme learning machine (ELM). First, the three‐phase output current is processed by the signal reconstruction method to eliminate the effect of load fluctuation, the average value of low frequency coefficients and wavelet entropy is extracted from the reconstructed three‐phase currents using the improved wavelet packet transform, and the fault feature vector is constructed by fusing the above two feature parameters. Second, the parameters of the ELM fault diagnosis model are optimized using WOA. Finally, the fault feature vector is added in the SR‐WOA‐ELM model to obtain the fault diagnosis results. Through simulation and experimental verification, the model can accurately identify the single‐tube and double‐tube faults of the inverter and is not affected by load fluctuations.

A single-phase full-bridge soft-switching inverter circuit with an auxiliary resonant circuit

A new topological structure is proposed in this article for the traditional single-phase full-bridge inverter circuit by adding an auxiliary synchronizing resonant circuit. Without extra switching transistors, the complexity of the control circuit is simplified while enabling zero voltage switching (ZVS) functionality. The significance of this proposed topology is that the switching transistors of all bridge arms are sharing one common synchronizing unit which is constructed with an absorbing inductor and capacitor. In this way, the added-on components can be substantially reduced for the main switching transistor circuit. By utilizing a big-volume capacitor as the constant voltage source, the sourceless energy feedback unit can minimize the switching losses. In the meantime, the proportional-resonant feedback circuit can modify the sinusoidal pulse width modulation (SPWM) duty ratio to stabilize the output current. In the PSIM power electronic simulation software environment, the operation of the soft-switching inverter circuit is analyzed to demonstrate our proposed topology can reduce the on-off switching losses as expected for the switching transistors of the soft-switching inverter circuit.

A Bootstrap Drive and Level Shifting Method for Buck-boost Converter with NMOS as the Main Switch Transistor

In the design of DC-DC power supply, compared with a P-type metal oxide semiconductor field effect transistor (PMOS) with the same width-to-length ratio, N-type metal oxide semiconductor field effect transistor (NMOS) as the main switching transistor greatly reduces the on-off loss and improves the conversion efficiency of the system. This article introduces a gate voltage bootstrap and level shifter circuit for a Buck-Boost DC-DC converter with NMOS main switching transistor. The drive voltage between the gate and the source pole of the main switch transistor can be stabilized, which is independent of the switch junction voltage (V SW) and solves the problem that the drive voltage of the gate is too high or too low due to the influence of the bootstrap voltage in the traditional structure. Based on the 0.18 μm BCD process, the circuit design and physical implementation of the proposed method are verified. The test results show that the bootstrap drive circuit functions normally and the bootstrap drive voltage is about 5 V when the input voltage is 2.9~4.5 V and the output voltage is −2~-5 V. In addition, the proposed gate-level shifting circuit can reduce the drive delay of the main switch transistor to less than 12 ns.

Design of a High Speed Electro-optic Q-switch Circuit for Aerospace Applications

In order to meet the requirements of high amplitude and high speed of electro-optic Q-switch voltage, a high speed electro-optic Q-switch circuit for aerospace applications is designed. According to the principle of Marx generator, the circuit uses a high speed driving chip to drive the switching transistor to conduct. The charge of the primary energy storage capacitor of the pulse transformer is quickly released, and the secondary induced voltage drives the switches of the Marx generator to open quickly and synchronously. By utilizing the fast and synchronous opening of MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), cascaded discharge is carried out on the energy storage capacitors of the 8th order Marx generator circuit, thereby outputting high voltage pulse signal. The experimental results show that the Marx generator has maximum boost output range of 4000V and high voltage pulse rise time of less than 30ns. Compared to traditional pulse transformer control methods, the Q-switch voltage rise time is reduced by nearly 40ns. The internal components of circuit meet the requirements of multiple indicators such as anti-irradiation space environment, and have the characteristic of short output high voltage rise time, which can provide high speed and high voltage driving pulses for the electro-optic Q-switch crystal inside the laser cavity.

Influence of avalanche transistor switching mode on waveform characteristics of solid-state pulse source.

The design of the Marx circuit based on avalanche transistors (ATs) is one of the effective techniques for developing solid-state pulse sources to generate nanosecond pulses. However, the influence of the avalanche transistor as a switching device on the output pulse characteristics is still unclear. In this study, investigating the switching mechanism of the AT with a mixed-mode simulation of the semiconductor device has been accomplished. An experiment has checked the simulation model's transient switching characteristics. The switching mechanisms of ATs in the Marx circuit were divided into base triggering mode (BTM) and voltage ramp mode (VRM). This paper proposes a modified circuit for adjusting the output pulse parameters of solid-state pulse sources. The results show that to satisfy the simulation accuracy, the width parameter of the AT model in the BTM must be 100μm, much less than the actual physical size. Because of the higher electric field when the initial impact ionization occurs, the AT operates at a higher switching speed in the VRM than in the BTM. In addition, since the carriers of initial impact ionization locate at the p-n0 interface or the n0-n+ interface, the AT switching process will oscillate in the VRM. All ATs in the modified Marx circuit switch to operate in the BTM. The leading edge of the output pulse increases from 275 to 1125ps, and the pulse trailing oscillation has disappeared. The research results provide an important technical means for optimizing the output waveform of solid-state pulse sources.

DEVELOPMENT OF THE POWER SUPPLY AND CONTROL SYSTEM FOR THE HEMODIALYSIS MACHINE

The article describes new approaches to creating an autonomous compact system with automatic control for hemodialysis. It is proposed to organize a closed circuit for cleaning the dialysis solution using an electrolytic regenerator as a function of the concentration of urea in it. The functional diagram of the created system is presented and described. To power the regenerator, ensure thermal stabilization of the solution, and power auxiliary electronic and electrical equipment, a multi-channel power supply and control system for the hemodialysis machine based on high-frequency magnetic amplifiers has been developed and researched. The advantages of power switches based on high-frequency magnetic amplifiers in comparison with transistor switches, including in the construction of controlled power sources, are given. The principle of operation of the voltage regulator on high-frequency magnetic amplifiers is described. Theoretical and experimental oscillograms are given. Photographs of the experimental unit as well as an industrial sample of the multi-channel power supply and control system of the hemodialysis machine are provided. Their main technical characteristics are given. Conclusions to the conducted work are formulated. Carrying out the regeneration of the dialysis solution significantly reduces its costs – 2 liters of solution, which is suitable for use for 6 months, is enough for the operation of the device. Existing hemodialysis machines are a stationary open system using a single-use dialysis solution at a rate of up to 35 l/h, which ties the machine to stationary clinical conditions. Introducing feedback on the concentration of urea in the dialysis solution allows you to automate the blood purification procedure, as well as automatically complete hemodialysis at the necessary time, and also eliminates the dependence of the device on the conditions of the hospital.

TESLA SWITCH OF 4 BATTERIES BASED ON THE ARDUINO UNO BOARD

The paper considered the theoretical information of generators for several power sources, schematic their solutions, and the main disadvantages and advantages. A generator for 4 batteries based on field-effect transistors with optical galvanic isolation and a clock generator built on the basis of the Atmega328 microcontroller, which is part of the Arduino Uno device, was studied. The result of the study was the confirmation of the existence of the "Tesla-switch" effect. A program code was developed for the alternate switching of six transistor switches of the optical decoupling. The structural diagram of the device was studied, and the influence of the generator frequency and the consumed power of the load on the output parameters of the device were determined. The considered idea of energy saving and environmental friendliness of power supply systems is relevant, in particular in cases of blackouts.

Device-circuit co-design of memristor-based on niobium oxide for large-scale crossbar memory

Memristor-based crossbar architecture emerges as a promising candidate for 3-D memory and neuromorphic computing. However, the sneak current through the unselected cells becomes a fundamental roadblock to their development, resulting in misreading and high power consumption. In this regard, we theoretically investigate the Pt/Ti/NbO2/Nb2O5−x/Pt-based self-selective memristor, which combines the inherent nonlinearity of the NbO2 switching layer and the non-volatile operation of the Nb2O5−x memory layer in a single device. The results show that the Pt/Ti/NbO2/Nb2O5−x/Pt-based self-selective memristor offers the sneak current of 310 nA, selectivity of around 174, and on/off current ratio of 75, compared to the sneak current of approximately 70 μA, selectivity of about 4.02, and on/off current ratio of around 1.55 for the Pt/Ti/Nb2O5−x/Pt-based memristor device. Our self-selective memristor minimizes the sneak current, but a small on/off current ratio limits their readout margin and power efficiency for crossbar array size greater than 4KB. Further, we demonstrate that breaking down a large-scale crossbar array into smaller subarrays and separating them by transistor switches, called the split crossbar array, is a more efficient way of achieving a practical size crossbar array with improved readout margin and power efficiency. Our results shed light on the potential of the Pt/Ti/NbO2/Nb2O5−x/Pt-based self-selective memristor and explore the split crossbar array architecture as a practical solution to augment readout margins and power efficiency in a large-scale crossbar array.

Optimization of switching losses of the Weinberg converter

DC-DC converters are widely used in hybrid power supply systems. A buffer source of electrical energy (most often a battery bank) and its charging and discharging devices are integral parts of such systems. In systems where the battery bank voltage is less than the DC-bus voltage and galvanic isolation is not required, the Weinberg converter is widely used as a discharge device, for example, in spacecraft power supply systems. The current trend in the development of hybrid power supply systems is to increase the power density of the system. Increasing the operating frequency is the simplest and most effective way to increase the power density of converter. A differential characteristic of this converter is the zero-current switching (ZCS) of transistors, which occurs due to the influence of the leakage inductance of coupled-inductors and the leakage inductance of the transformer. The paper presents an analysis of the influence of leakage inductances on the operation of the converter and a method of determining a level of turn on switching losses of transistors, which allows to ensure the necessary level of efficiency of the converter. The results of simulation modeling of the converter confirm the effectiveness of this method.

Three-Dimensional Integration of Switching and Light-Sensitive Organic Transistors in Solution Processes for Flexible High-Resolution Active-Matrix Optical Imager

Three-Dimensional Integration of Switching and Light-Sensitive Organic Transistors in Solution Processes for Flexible High-Resolution Active-Matrix Optical Imager

Compact Bandwidth-Enhanced 180-Degree Phase Shifter Using Edge-Coupled Multi-Microstrip and Artificial Transmission Line.

Compactness has obtained sufficient importance in wideband phase shifter design considerations, as it is directly related to fabrication cost. In this paper, a novel structure was presented to create compact broadband 180-degree phase shifter, which has the advantages of enhanced bandwidth and significantly reduced chip area. The proposed configuration consists of edge-coupled multi-microstrip lines (ECMML) and an artificial transmission line (ATL) with dual-shorted inductors, both of which have the periodic shunt load of capacitors. The ECMML can provide a high coupling coefficient, leading to an increase in the bandwidth, while the introduced capacitors can greatly reduce the line length (35.8% of the conventional method). To verify the relevant mechanisms, a wideband switched network with compact dimensions of 0.67 × 0.46 mm2 was designed via 0.15-micrometer GaAs pHEMT technology. Combined with the measured switch transistor, it was shown that the proposed phase shifter exhibits an insertion loss of less than 2 dB, a return loss of greater than 12 dB, a maximum phase error of less than 0.6° and a channel amplitude difference of less than 0.1 dB in the range of 10 to 20 GHz.

(Invited) NiO/ β-(Al x Ga1-x )2O3 /Ga2O3 Heterojunction Lateral Rectifiers with Reverse Breakdown Voltage > 7kV

There is significant recent interest in development of Ga2O3 power devices due to their capability for high temperature operation, reduced on-state and switching losses due to lower on-resistance for high voltage devices, and potentially higher frequency switching capability. These are targeted for renewable energy transmission systems, electric vehicle (EV) traction inverter and motor control systems, fast charging stations and more electric aircraft. Since the efficiency of EV powertrain inverters is partially determined by the efficiency of the switching transistors, it is of interest to examine ultra-wide-bandgap semiconductor electronics. The successful development of these power transistors is expected to significantly increase the longevity of a battery charge and the resultant cost of an EV.In this work, NiO/ β-(Al x Ga1-x )2O3 /Ga2O3 heterojunction lateral geometry rectifiers with diameter 50-100 µm exhibited maximum reverse breakdown voltages >7kV, showing the advantage of increasing the bandgap using the β-(Al x Ga1-x )2O3 alloy. This Si-doped alloy layer was grown by Metal Organic Chemical Vapor Deposition with an Al composition of ~20%. On state resistances were in the range 50-2180 Ω.cm2, leading to power figures-of-merit up to 0.72 MW.cm-2. The forward turn-on voltage was in the range 2.3-2.5 V, with maximum on/off ratios >700 when switching from 5V forward to reverse biases up to -100V. Transmission line measurements showed the specific contact resistance was 0.12 Ω.cm2. The breakdown voltage is among the highest reported for any lateral geometry Ga2O3-based device. Figure 1

СПОСОБИ ПІДВИЩЕННЯ ЕНЕРГОЕФЕКТИВНОСТІ СПЕЦІАЛІЗОВАНИХ ПЕРЕТВОРЮВАЧІВ ЕЛЕКТРОЕНЕРГІЇ ДЛЯ СУЧАСНИХ ІМПУЛЬСНИХ ТЕХНОЛОГІЙ

The article examines the proposed power electronics devices with an assessment of their basic quality indicators and functional purpose. The following of these devices have been identified, the use of which increases the e nergy efficiency of electrical networks the most. It is shown that these devices, due to their improved functional and parametric data, are also widely used in electrical consumer devices. Here are some of the mentioned devices. Combined and Controlled Latour-Gretz Rectifiers, Magnetic Semiconductor Pulse Regulators, DC/DC Pulse Converters, DC/AC Converters, DC/AC Converters, Full Thyristor Transistor Switch - VTS, Controlled Magneto-Semiconductor Generator pulses, an improved structural diagram of a magnetic semiconductor pulse generator. It was concluded that the following quality indicators of the above devices are the most acceptable for increasing the energy efficiency of electrical networks on the part of devices that are powered by them: high efficiency; improved electromagnetic compatibility; protection against short circuits and switching overvoltages; controllability according to load requirements; buffer resistance against interruption of the input current. Ref. 7, fig. 7. Keywords: energy efficiency of electrical networks, combined and controlled Latour-Gretz rectifiers, magnetic semi-conductor regulators and pulse generators, pulse converters DC/DC, DC/AC.

Optimizing the initial weights of a PID neural network controller for voltage stabilization of microgrids using a PEO-GA algorithm

This paper proposes an adaptive PID neural network (PIDNN) controller for direct and quadrature voltage control of three-phase inverters for islanded microgrids. A hybrid metaheuristic optimization algorithm is proposed for the initial weight selection of the proposed PIDNN controller using a discrete-time simulation model incorporating the nonlinearity of the insulated gate bipolar transistor (IGBT) or metal oxide semiconductor field effect transistor (MOSFET) switches of the inverter. The proposed hybrid optimization (HO) approach is a combination of population extremal optimization (PEO) and genetic algorithm (GA). It turned out that the proposed HO-PIDNN control scheme excelled the PEO, GA, and particle swarm optimization-based PIDNN controllers in terms of the objective function value, which is composed of the integral time absolute tracking error of the output voltage and a chattering penalty factor. Also, the control system outperformed the model reference adaptive PID control technique from the literature.

Room-temperature fabrication of flexible oxide TFTs by co-sputtering of IGZO and ITO

Amorphous oxide semiconductors, especially indium gallium zinc oxide (IGZO), have been widely studied and obtained significant progress in flexible thin-film transistors (TFTs) due to the high carrier mobility and low deposition temperature. However, a further annealing step is generally required to activate electrical properties and improve the device performance, which limited their applications in flexible electronics. In this study, we achieved flexible TFTs and arrays using co-sputtered IGZO and indium tin oxide (ITO) as channels deposited at room temperature without post-annealing. It was found that better transistor switching properties could be effectively achieved by regulating the sputtering power of ITO in the co-sputtered deposition. The device performance is comparable to that of the conventional oxide TFTs with high annealing temperatures (⩾300 °C), exhibiting a high saturation mobility (μ sat) of 15.3 cm2 V−1s−1, a small subthreshold swing (SS) of 0.21 V dec−1, and a very high on–off ratio (I on/off) of 1011. In addition, a 12 × 12 flexible TFT array was achieved with uniform performance owing to the low-temperature processing advantage of this technique. The flexible TFTs exhibited robust mechanical flexibility with a minimum bending radius of 5 mm and bending cycles up to 1000. Furthermore, an inverter based on co-sputtered IGZO and ITO was demonstrated with the maximum gain of 22. All these achievements based on the proposed TFTs without post-annealing process are expected to promote the applications in advanced flexible displays and large-area integrated circuits.